This study intends to recruit 90-100 constipated participants aged 25-50 years, including an equal number of males and females, from the faculty and logistics staff of Capital Medical University. Participants will be randomly divided into an intervention group (55-60 individuals) and a control group (35-40 individuals). The intervention group will consume 250 mL of Mengniu Daily Fiber Oat Milk daily for 4 weeks, while the control group will not receive oat milk intervention. Both groups will maintain their original lifestyles, including diet, sleep, and exercise, throughout the study period. Baseline surveys, dietary surveys, blood and urine routine tests, blood biochemical indices, and intestinal flora detection will be conducted before and after the intervention. Defecation status will be recorded, and gastrointestinal symptoms will be assessed using a Gastrointestinal Symptom Rating Scale. Statistical analysis will be performed to determine the laxative efficacy of oat milk.

Inclusion Criteria:

Clinical diagnosis of non-organic and habitual constipation;

Reduced defecation frequency;

Increased stool hardness;

Fewer than 4 bowel movements per week;

Exclusion Criteria:

Inability to take food orally or inability to comply with the required intake of the test product;

Known allergy to oats or related products;

Unclear primary gastrointestinal complaints;

Physical weakness that prevents participation in the trial;

History of surgery within the past 30 days that may cause constipation；

Recent constipation caused by severe organic gastrointestinal lesions (e.g., colon cancer, severe enteritis, intestinal obstruction, inflammatory bowel disease);

Constipation accompanied by significant abdominal pain;

Acute gastrointestinal diseases within the past 30 days;

Severe systemic diseases involving the cardiovascular, hepatic, renal, or hematopoietic systems;

Ongoing treatment for comorbid conditions that may interfere with study participation;

Recent use of substances related to the tested function that may influence outcome measurements.